.Box {
    float: left;
    width: 70%;
    text-align: center;
    margin-left: 15%;
    margin-right: 15%;
    margin-top: 70px;
    margin-bottom: 20px;
}

@media screen and (max-width:640px) {
    .Box {
        margin-left: 5%;
        margin-right: 5%;
        margin-top: 80px;
        margin-bottom: 0px;
        width: 90%;
        margin: 6%;
    }
}

.box1 {
    width: 100%;
    height: 100%;
    float: left;
    animation: myfirst .4s;
    -moz-animation: myfirst 4s;
}

@keyframes myfirst {
    0% {
        opacity: 0;
    }
    25% {
        opacity: 1;
    }
    75% {
        opacity: 1;
    }
    100% {
        opacity: 0;
    }
}

@-moz-keyframes myfirst {
    0% {
        opacity: 0;
    }
    25% {
        opacity: 1;
    }
    75% {
        opacity: 1;
    }
    100% {
        opacity: 0;
    }
}
